X-ray CT (Computed Tomography) imaging is normally performed in a lying state in which a patient lies on a bed. In recent years, CT imaging in a standing or sitting state is demanded in diagnosis of swallowing or the like.
When performing CT imaging in the standing or sitting state, it is necessary to make a patient stand at an appropriate position to prevent contact between the patient and the gantry. It is also necessary to determine whether the patient is standing at an appropriate position. However, a method of making a patient stand at an appropriate position and a method of determining whether the patient is standing at an appropriate position when performing CT imaging in the standing or sitting state are not established yet.